Process for the removal of mercaptans

Abstract

A process for treating a full boiling range naphtha is disclosed in which the mercaptans and diolefins are removed simultaneously in a debutanizer distillation column reactor. The mercaptans are reacted with the diolefins to form sulfides which are higher boiling than the C 4 and lighter portion of the naphtha which is taken as overheads. The higher boiling sulfides are removed as bottoms along with any C 5 and heavier materials. The bottoms are preferably taken to a splitter where a portion is taken as overheads and a heavier portion is recovered with the sulfides. This reduced volume of naphtha may be hydrogenated to convert the sulfides to H 2 S and diolefins, which may be hydrogenated to olefins and alkanes.

The invention claimed is:  
     
       1. A process for removing mercaptans from a full boiling range naphtha hydrocarbon stream, comprising the steps of: 
       (a) feeding a full boiling range naphtha stream containing mercaptans and diolefins to a distillation column reactor above a catalyst bed containing an alumina supported Group VIII metal;  
       (b) feeding an effectuating amount of hydrogen to said distillation column reactor below the catalyst bed;  
       (c) concurrently in said distillation column reactor  
       (i) contacting diolefins and mercaptans contained within said naphtha stream in the presence of hydrogen in a distillation reaction zone in the lower section of said distillation column reactor thereby reacting a portion of said mercaptans with a portion of the diolefins to form sulfide products and distillate product and  
       (ii) separating said sulfides from said distillate product by fractional distillation;  
       (d) withdrawing distillate product from said distillation column reactor at a point above said distillation reaction zone, said distillate product having a reduced mercaptan content; and  
       (e) withdrawing a portion of said naphtha hydrocarbon stream and sulfide products from said distillation column reactor at a point below said distillation reaction zone.  
     
     
       2. The process according to claim  1  wherein said full boiling range naphtha stream is a cracked naphtha distillate containing a C 4  and lighter fraction and a C 5  and heavier fraction, said C 4  and lighter fraction is removed as overheads from said distillation column reactor and said C 5  and heavier fraction is removed as bottoms from said distillation column reactor along with said sulfide product. 
     
     
       3. The process according to claim  1  wherein there is a molar excess of diolefins to mercaptans. 
     
     
       4. The process according to claim  3  wherein substantially all of said mercaptans are reacted with diolefins to form sulfide products and said distillate product is substantially mercaptan free. 
     
     
       5. The process according to claim  3  wherein substantially all of said excess of diolefins not reacted with mercaptans are hydrogenated to mono-olefins. 
     
     
       6. The process according to claim  1  wherein said naphtha hydrocarbon stream and sulfide products of step (e) are fractionated to produce a naphtha hydrocarbon fraction free of sulfide products and naphtha hydrocarbon fraction containing said sulfide products. 
     
     
       7. The process according to claim  6  wherein said naphtha hydrocarbon fraction containing said sulfide products is hydrogenated to produce H 2 S. 
     
     
       8. The process according to claim  1  wherein a second catalyst bed containing an alumina supported Group VIII metal is positioned above said full boiling range naphtha stream wherein methyl mercaptan is contacted with diolefin and reacted to form sulfide products. 
     
     
       9. The process according to claim  1  wherein the hydrogen partial pressure is in the range of 0.1 to 30 psi. 
     
     
       10. The process according to claim  9  wherein the total pressure is 50-200 psig. 
     
     
       11. The process according to claim  10  wherein the temperature in said distillation reaction zone is in the range of 100 to 400° F.